Methods of inspecting a lithography template

Abstract

A method for forming imprint lithography templates is described herein. The method includes forming a masking layer and a conductive layer on a substrate surface. The use of a conductive layer allows patterning of the masking layer using electron beam pattern generators. The substrate is etched using the patterned masking layer to produce a template.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS[0001]The present application is a divisional patent application of, and claims priority from, U.S. patent application Ser. No. 10 / 136,188, filed May 1, 2002, entitled METHODS OF MANUFACTURING A LITHOGRAPHY TEMPLATE and listing Ronald Voisin as inventor. U.S. patent application Ser. No. 10 / 136,188 is incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention generally relates to lithography templates. More particularly, certain embodiments of the invention relate to the formation of imprint lithography templates fabricated by pattern generators.[0004]2. Description of the Relevant Art[0005]For imprint lithography, a relief pattern in a template is used, in conjunction with monomers / polymers to imprint a desired pattern into monomers / polymers on the surface of a substrate (e.g., semiconductors, dielectric materials, magnetic or optoelectonic materials.) The processes com...

AI Technical Summary

Benefits of technology

[0014]Described herein are methods for making templates for use in lithography systems. The methods described herein are directed to the production of templates with minimal undercut, low defect density, and improved inspectability. These methods are particularly useful for the formation of templates having features that have a lateral feature size of less than about 200 nm. For ultraviolet light curing applications, a template may be formed from an ultraviolet light transmissive substrate. The ultraviolet light transmissive substrate may be formed from a variety of materials (e.g., quartz). Initially, a conductive polysilicon layer is formed on the surface of the substrate. Upon the conductive polysilicon layer, a masking layer is formed. Masking layer may be composed of a photoresist material. The masking layer is partially patterned and developed. During the development process portions of the masking layer are removed to reveal portions of the underlying conductive polysilicon layer. The masking layer may be patterned using a pattern generator. Examples of pattern generators include electron beam pattern generators and laser beam pattern generators. The exposed portions of the conductive polysilicon layer may be etched using an anisotropic etch procedure. The etching of the conductive polysilicon layer is continued until portions of the underlying substrate are exposed. The exposed portions of the underlying substrate may be etched using an anisotropic process. Removal of the remaining portions of the conductive polysilicon layer and the masking layer is performed after the etching of the substrate is complete.

[0015]The use of a conductive polysilicon masking layer may allow increased contrast during inspection processes. In one embodiment, the thickness of the conductive polysilicon layer may be set to maximize the contrast between the template and the conductive polysilicon layer during a light inspection process. Alternatively the conductive polysilicon layer may have a predetermined thickness based on processing requirements. In this situation, the wavelength of light used for the inspection processed may be altered to maximize the contrast between the template and the conductive polysilicon layer.

[0017]In an alternate embodiment, a substrate is formed having a base layer, an etch stop layer and an upper layer, with the etch stop layer disposed between the base layer and the upper layer. The resulting substrate may be etched using either of the techniques described above. Etching of the substrate may be controlled by the etch stop layer. The etch stop layer may be formed of a material that has a substantially different etching rate than the upper layer. Because of this difference in etch rate, the etch stop layer may provide a more uniform depth of etching.

Problems solved by technology

Etching of the opaque material may be difficult if the opaque material is a metal.

Many metals produce particles and aggregates during a dry etch process which may be deposited on the substrate creating defects in the pattern.

A wet etch process may be used to avoid the deposition of particles, however, wet etching processes suffer from undercutting problems for very small features.

A problem with trying to apply photomask manufacturing process for the manufacture of imprint lithography templates is that the completed photomask tends to have a critical feature size that is generally larger than the feature size that the pattern generation equipment can create.

However, the isotropic etching undercuts the photoresist pattern by about the thickness of the opaque layer or more and makes the openings in the opaque pattern larger than the original openings in photoresist pattern.

For previous generations of semiconductor devices, the undercutting, while not desirable, was acceptable.

However, as feature sizes become smaller, the size of the undercut becomes more difficult to accommodate, and higher resolution generations of integrated circuits having smaller feature sizes have found the undercutting unacceptable.

Heavy metal compounds that are liberated during the dry etch processes, however, inherently accrete and precipitate to create defects on the photomask surface.

Additionally there tends to be relatively poor etch selectivity (between the photoresist pattern and the opaque layer) that results in some undercut because the dry etch widens the openings.

However, this technique has drawbacks.

The indium tin oxide layer, while transparent at visible wavelengths, is generally opaque at deep ultraviolet wavelengths thereby limiting the use of deep ultraviolet wavelengths in imprint lithography that would use such templates.

The greater depth of the recesses in an imprint lithography template may make inspection difficult.

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